Nike, which initially stood by Armstrong, dropped him Wednesday with a terse statement citing what it called "seemingly insurmountable evidence" that he participated in doping.

Photos: Lance Armstrong's rise and fall 28 photos

Photos: Lance Armstrong's rise and fall28 photos

Lance Armstrong's rise and fall – After denying the allegations for years, cyclist Lance Armstrong admitted to using performance-enhancing drugs. As a result, he was stripped of his seven Tour de France titles and an Olympic bronze medal. Click through the gallery for a look at his life and career.

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Photos: Lance Armstrong's rise and fall28 photos

Lance Armstrong's rise and fall – Armstrong, 17, competes in the Jeep Triathlon Grand Prix in 1988. He became a professional triathlete at age 16 and joined the U.S. National Cycling Team two years later.

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Photos: Lance Armstrong's rise and fall28 photos

Lance Armstrong's rise and fall – Armstrong wins the 18th stage of the Tour de France in 1995. He finished the race for the first time that year, ending in 36th place.

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Photos: Lance Armstrong's rise and fall28 photos

Lance Armstrong's rise and fall – Armstrong rides at the Ikon Ride for the Roses to benefit the Lance Armstrong Foundation in May 1998. He established the foundation to benefit cancer research after he was diagnosed with testicular cancer in 1996. After treatment, he was declared cancer-free in February 1997.

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Photos: Lance Armstrong's rise and fall28 photos

Lance Armstrong's rise and fall – Armstrong leads his teammates during the final stage of the 1999 Tour de France.

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Lance Armstrong's rise and fall – Armstrong takes his honor lap on the Champs-Élysées in Paris after winning the Tour de France for the first time in 1999.

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Lance Armstrong's rise and fall – After winning the 2000 Tour de France, Armstrong holds his son Luke on his shoulders.

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Lance Armstrong's rise and fall – Armstrong rides during the 18th stage of the 2001 Tour de France. He won the tour that year for the third consecutive time.

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Photos: Lance Armstrong's rise and fall28 photos

Lance Armstrong's rise and fall – Armstrong celebrates winning the 10th stage of the Tour de France in 2001.

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Lance Armstrong's rise and fall – After winning the 2001 Tour de France, Armstrong presents President George W. Bush with a U.S. Postal Service yellow jersey and a replica of the bike he used to win the race.

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Lance Armstrong's rise and fall – Armstrong celebrates on the podium after winning the Tour de France by 61 seconds in 2003.

Lance Armstrong's rise and fall – After his sixth consecutive Tour de France win, Armstrong attends a celebration in his honor in front of the Texas State Capitol in Austin.

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Lance Armstrong's rise and fall – Armstrong arrives at the 2005 American Music Awards in Los Angeles with then-fiancee Sheryl Crow. The couple never made it down the aisle, splitting up the following year.

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Lance Armstrong's rise and fall – Armstrong holds up a paper displaying the number seven at the start of the Tour de France in 2005. He went on to win his seventh consecutive Tour de France.

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Lance Armstrong's rise and fall – Armstrong testifies during a Senate hearing in 2008 on Capitol Hill. The hearing focused on finding a cure for cancer in the 21st century.

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Lance Armstrong's rise and fall – In 2009, Armstrong suffered a broken collarbone after falling during a race in Spain.

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Lance Armstrong's rise and fall – Young Armstrong fans write messages on the ground ahead of the 2009 Tour de France. He came in third place that year.

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Lance Armstrong's rise and fall – Armstrong launches the three-day Livestrong Global Cancer Summit in 2009 in Dublin, Ireland. The event was organized by his foundation.

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Lance Armstrong's rise and fall – In May 2010, Armstrong crashes during the Amgen Tour of California. That same day, he denied allegations of doping made by former teammate Floyd Landis.

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Lance Armstrong's rise and fall – Armstrong looks back as he rides during the 2010 Tour de France.

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Lance Armstrong's rise and fall – Armstrong's son Luke; his twin daughters, Isabelle and Grace; and his 1-year-old son, Max, stand outside the Radio Shack team bus on a rest day during the 2010 Tour de France.

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Lance Armstrong's rise and fall – Armstrong finished 23rd in the 2010 Tour de France. He announced his retirement from the world of professional cycling in February 2011. He said he wanted to devote more time to his family and the fight against cancer.

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Lance Armstrong's rise and fall – The frame of Armstrong's bike is engraved with the names of his four children at the time and the Spanish word for five, "cinco." His fifth child, Olivia, was born in October 2010.

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Lance Armstrong's rise and fall – Armstrong competes in the 70.3 Ironman Triathlon in Panama City, Florida, in February 2012. He went on to claim two Half Ironman triathlon titles by June of that year.

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Lance Armstrong's rise and fall – Armstrong addresses participants at the Livestrong Challenge Ride on October 21, 2012, days after he stepped down as chairman of his Livestrong cancer charity.

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Lance Armstrong's rise and fall – International Cycling Union President Pat McQuaid announces the decision to strip Armstrong of his seven Tour de France wins and ban him from the tournament for life on October 22, 2012. "Lance Armstrong has no place in cycling," he said.

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Lance Armstrong's rise and fall – In January 2013, Armstrong speaks with Oprah Winfrey about the controversy surrounding his cycling career. He admitted, unequivocally and for the first time, that he used performance-enhancing drugs while competing.

Hamilton: I doped for Lance Armstrong

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Nike severs ties with Lance Armstrong

Hours later, brewery giant Anheuser-Busch followed suit, saying it will let Armstrong's contract expire at the end of the year. Nike and Anheuser-Busch said they still plan to support Livestrong and its initiatives.

The American Cancer Society, which has had a long relationship with Armstrong, said only that it would continue to collaborate with Livestrong.

Armstrong walked away as chairman of the Livestrong cancer charity "to spare the foundation any negative effects as a result of controversy surrounding my cycling career," according to a statement posted to the group's website.

He will remain on the charity's board of directors, but he will turn over the reins to founding chairman Jeff Garvey.

The seven-time Tour de France winner has consistently denied the claims, and legions of fans and corporate supporters had backed him -- until now.

Armstrong founded the Livestrong charity in 1997 after his own successful treatment for testicular cancer that had spread to his brain and lungs. He came back from the disease seemingly stronger than ever, winning the first of his seven Tour de France titles less than three years after he was diagnosed in 1996.

His success inspired cancer patients worldwide, spreading his reach far beyond the insular world of cycling and cementing his place in celebrity culture. He became rich, dated a rock star and appeared in movies. The bright yellow "LIVESTRONG" wristbands distributed by his charity became a potent symbol for perseverance in the face of adversity.

People should look to that legacy in assessing Armstrong, Livestrong's president said.

"Lance's devotion to serving others whose lives were irrevocably changed by cancer, as his was, is unsurpassable," Doug Ulman said in a statement issued after Wednesday's announcement. "We are incredibly proud of his record as an advocate and philanthropist and are deeply grateful that Lance and his family will continue to be actively involved with the Foundation's advocacy and service work."

But a long chain of accusations has trailed Armstrong.

In 2002, a 21-month investigation into allegations that Armstrong's team used banned substances during the 2000 Tour de France closed after finding no evidence of illegal drug use.

He later sued the author of a book that accused him of having used performance-enhancing drugs and the International Cycling Union cleared him of 1999 doping allegations in a 2006 report.

In 2010, former teammate Floyd Landis accused him of doping. Federal prosecutors also looked into the allegations but closed their case in Feburary without pressing charges.

That's when USADA began its investigation.

In its report, released last week, the anti-doping agency made public testimony from Armstrong's teammates and others who said Armstrong was among team members who used banned performance-enhancing substances and tried to hide it from testing officials.

The report is part of USADA's request to international cycling officials to strip Armstrong of his seven Tour de France titles. The International Olympic Committee is also reviewing the evidence and could consider revoking Armstrong's bronze medal from the 2000 Sydney games. Armstrong is already banned from competing in events sanctioned by U.S. Olympic governing bodies.

Armstrong has said he never has failed a drug test and has consistently denied participating in any banned practices. Armstrong's lawyer, Tim Herman, called the report last week a "one-sided hatchet job" and a "government-funded witch hunt." He did not return a call on Wednesday.

So far, Armstrong's woes haven't affected the charity's ability to raise money, according to Livestrong spokeswoman Katherine McClane. Donations to the charity have actually boomed since August, when Armstrong announced he was ending his legal fight to stop USADA's investigation, she said last week.

That's because, according to McClane, the charity's main audience -- cancer patients and their families -- isn't troubled by Armstrong's woes.

"The last thing that's going to enter your mind is news from the cycling world," McClain said Wednesday.

According to Livestrong, Armstrong has helped raise nearly $500 million, including $6.5 million of his own, for cancer research, treatment and support in his role as Livestrong founder and has helped "dispel the stigma and misconceptions about the disease."

Livestrong will need to find a new way to present itself to the world without Armstrong as its face, said Eric Martin, a partner with Boost Partners, a Richmond, Virginia, strategic consulting firm.

How? Focus on "real-world heroes who have faced down cancer while loving a sport more than the spotlight," Martin said.

"At this point, what they need to do is re-establish the authenticity of their cause and the way to do that, in my opinion, is to reconnect with what people really admire in their heroes," Martin said.

Howard Bragman, an expert in crisis communications and vice chairman of Reputation.com, an online reputation management company in Los Angeles, said the future of Livestrong is uncertain.

"I personally hope that Livestrong is stronger than Lance Armstrong because they have done -- and continue to do -- amazing work for people with cancer," he told CNN in a telephone interview.

But he said he had little doubt that the impact on Armstrong would be devasating. "It doesn't get any worse than this, OK?" he told CNN in a telephone interview. "Imagine losing the prestige of all your Tour de France titles, millions in endorsements, stepping down from the organization he loves and founded, that's been his public mission -- and, possibly the worst thing of all, which is public humiliation."